All those things down the left side of the main messenger window (alerts, etc.),

Contact Cards,

Backgrounds,

Winks,

Dynamic Display Pictures,

Ads

Any of the other useless 'features' I missed.

Live messenger is great and out of all the messenger clients I've ever used it's definately my favourite. But it could be so much better without all that extra stuff. Simplicity and performance should be your two most important features.